Currently it is not possible to invoke a re-indexing of facial recognition data at either the global or folder/collection level. For my purposes re-indexing at the folder and collection level would be sufficient.

Reason: when a face is removed from a previously indexed image it is not possible to automatically recognize faces other than reviewing many images and manually applying a face region.

Yes, this is a function that should be available. Had tagging completed on a catalog with over 30k images in LR5 and upgraded. Went through tagging with facial recognition and was nearly done (5k left) and lost all tags but a few faces. Now, I've lost all person tags, even the ones I had in LR5.

With a large catalog 200K+ images as I have this is an essential. Additionally we need some control over the granularity over the face detection - at the moment FR is missing 30-40% of faces. We need to be able to say 'try again' and search harder!

Also re-indexing needs to be in two flavours - start from scratch on the selected images and secondly and more importantly search for faces not previously found - without removing those previously found and labelled.

I see the inverse problem here occasionally (less than 1%) too: a face detection box that includes only a section of the background, or similar, which I have to manually delete. I've stared at several of these to try and see why Lightroom thinks there is a face there, and I just don't see it. It's like Lightroom is experiencing a strange computer version of pareidolia.

I fully agree. Lightroom needs two updates asap:
1) ability to rescan all photos for faces
2) ability to set granularity to the facial recognition function. There are currently approx 30-50% faces being missed in my photos. I am willing to manually deselect what is not a face rather than to have to go through all the photos to make sure there isnt a face missed

Additionally, I would welcome better selection management based on facial recognition. I currently cannot select 6 people and see only photo where they are all together.

Also, Lightroom found almost 30,000 faces in my photos. But it is terrible at grouping the faces together. I have many, many groups of my son in stacks of 4 or 5 photos, instead of 1 stack of hundreds of photos. Now that I have named a bunch of photos, perhaps reindexing would allow Lightroom to more intelligently create larger groups of photos of the same person?

David, it only stacks them if it's really pretty sure it's the same person. This means that you can generally name the stack without having to look inside.

If it bunched all of the guesses together, half of them would be wrong, but if you want to see that view, double click on a photo of your son and confirm them in the Similar section of the Person view. That view is a lot more relaxed about suggestions.

Victoria, I think you are confusing the guess window and the confirmed window. I've got the same as David. In the confirmed panel, a single stack for each of 4 persons (with a high number of hits inside), then 15 stacks of one person (i.e. same person and same name on stack) with a low numer of hits inside each. I've tried to drag one stack on top of the other for this same name, accepting to 'rename' in the process (though it is a rename to the same name), but to no avail. Do you have any tip for this problem?

Can we try some proper names for different UI elements? That might help us all be on the same page. At the top of the People view we have Named People then below we have Unnamed People. In the Single Person view, we have the Confirmed section at the top and then the Similar section. Where are you looking? Or screenshots would help greatly.

I have images taken moments apart of a model who doesn't move that are not merging together. There is something wrong with the algorithm to some extent. The photos can be next to each other 2 seconds apart and not perceptively different and it won't recognize them as the same person

Re-running face detection, globally and at the folder and selected photo(s) level, has to be a priority for the NEXT update. The "hit rate" for simply detecting faces in a photo (not identifying, just detecting that a face is there) is incredibly low. I'm seeing less than 50% success rate in detecting faces. Recognizing who is in each photo isn't performing well either, but failing to detect the only face in a portrait photo is a pretty big bug.

You may have to rotate them back, but this seems to trigger the Face reognition process again.

I made the big mistake of deleting the face catalogue accross my entire library after my PC virtually stopped responding. Apx 50,000 faces had been detected but not labelled, and the ID/naming process was so painfuly slow I figured what harm could it be starting fresh again. Little did I realise that face recogition was a one trick pony, and once run, couldn't be re run again. I'm sure many others have been tripped up by this, and find it hard to imagine how Adobe engineers could have designed the UI with such a glaring ommision.

I've tested this on small sets of 20-30 images using bulk select/actions. Rotating once triggers a rescan which picks up some faces, rotating back to original orientation forces another rescan which picks up the rest. Not the most elegant fix, but it works for me. :-)

You know, if I actually had the time (which I don't) it wouldn't be that hard to go into the LR6 database, find out which tables & fields are marking a photo as "skip_facial_recognition", and just unmark them en masse with an sql lite database editor. But, this should be Adobe's job. Thanks for the tip!

I just tried it, and it isn't working for me. I tried both a 360° rotation and a 90° left-then-right rotation.

I read elsewhere that this won't work if you manually delete a region that Lightroom automatically added because it sets a flag in its DB that says "I already checked that one," so it refuses to go and try again, apparently thinking it would just waste a bunch of CPU cycles doing something it has already done.

The problem with that logic is that Lightroom knows more about faces when you tell it to go and look for faces again, so it should be able to do a better job the second time around.

I was amazed not to find this re-scan functionality in the tutorial video so I had a look in the manual - and did not find it. Couldn't believe it so I searched and found the discussion - and this request which I believe is really needed for a smooth use of facial recognition.

Two issues:
a) Reindexing photos - having LR clear and re-draw face regions on photos to allow people to fix mistakes (undelete, etc.)
b) Forcing LR to re-run matching logic on 1000s of faces that it guesses matches incorrectly. I've tagged 20K faces and some individuals have 100s of example faces tagged. I still have about 15K faces to go, but the match accuracy on these last images is poor (maybe 10%) instead of getting better. I want force LR to rerun the comparison logic of these labeled faces considering the faces already tagged. LR asking if my blonde niece is my dark haired son may have been acceptable at the start of the process, but I have 5K images tagged with my son, and 300 images tagged of my niece. Mismatches at this point is unacceptable.
b) Picasa offers an adjustable scale of the criteria to make a match. Such a tool could be helpful.

It would also be very nice if the facial recognition software was aware of context, because a lot of photos are already tagged with names, just not connected to the faces. If someone's name is in the keywords, chances are that the face is them, not someone that looks vaguely like them.

It would also be nice to restrict the face matching to certain groups, I'm not going to have a lot of my aikido friends show up in a photoshoot at a dance, and not a lot of dancers will show up at a family gathering, and so forth.

I did a photo shoot this weekend. Is there a way to export the files as a separate catalog, then delete all facial recognition information from that catalog, re-start facial recognition on that catalog, and reimport it to my working catalog?

Facial Recognition in LR6 is very poor. Sometimes it does not put the square over the face even in a portrait. In an example folder of 120 photos, the suggested people rectangle was towards the upper left of the photo, unrelated to where the face was, in most photos. Moving the rectangle is a painful task, I have 120,000 photos in my catalog. Sometimes, LR6 guessed correctly even if only part of the face was visible. What then, if I accept, does that mess up all future matches. If I reject, how to I get it to look for the face again. If I move the rectangle, will I live long enough to do all 120,000 photos. Please fix this soon. It is potentially a great tool. Attached is a photo with a face that LR6 could not find.

Here is another photo that had faces LR6 could not find. These faces had previously been found in other photos. I am finding that LR6 tends to put the bounding rectangle at the upper left as in this photo and the one I posted previously: In other words LR6 has no clue whether there is a picture or not. Moving the rectangle and identifying the face, did not result in improved performance on similar photos.

I've just been doing some work in Google Picasa this morning - and it really hit home just how good Google's product is (especially for a free consumer app) and how bad Adobe's implementation is. Google have an amazingly good hit rate, it's super easy & fast to remove false matches and the process has little impact on other software features when using the program. Adobe really need to the their stuff together.